Process of working leather.



Nrrn STATES ATENT WILLI LISSAUER, or BERLIN, GERMANY, ASSIGNOR TOLEONHARD FRIED- LANDER, on SAME PLACE.

PROCESS OF WORKING LEATHER.

SPECIFICATION forming part of Letters Patent No. 680,604, dated August13, 1901.

Application filed June 10, 1899. Serial No. 720,071. (Specimens) To allwhom it may concern:

Be it known that I, WILLI LISSAUER, a subject of the King of Prussia,German Emperor, residing at the city of Berlin, Germany, have invented anew and useful Process of \Vorking Leather, of which the followingis aspeci-- fication.

My invention has relation to the treatment of leather with the object ofimproving its quality, in that it is rendered more elastic and flexibleand more durable.

Leather tanned by the more modern processes, especially the rapidprocesses, is, as is well known, much inferior in quality,in so far asflexibility and durability are concerned, to leather which has beentanned by the older processes, requiring longer periods of time in theircompletion.

The elasticity or flexibility of hides and skins is due to certainpeculiar miscroscopic filaments, chiefly tubular tissues, the elastincomposed, of an albuminous substance free from sulfur. These elastintissues are not as readily affected by the tanning agent as the othertissues of the hide or skin and in the socalled rapid processes are butimperfectly tanned and become filled with the tanning solution, whichwhen the leather is exposed to moisture is dissolved out, thusdestroying the flexibility and elasticity of the said elastin tissues. Ihave discovered that leather, and particularly leather of inferiorquality, can be so treated as to eitectually protect the elastin tissuesagainst the action of moisture by reacting upon them with bisulfld ofcarbon or with a hydrocarbon capable of dissolving a resin, as of thegroup O H and holding the resin in solution in suitable proportions, thesolvent acting upon these tissues and preparing the same for thereception of an infinitely thin coating of resin, whereby these fibersor filaments are practically waterproofed, and practice has shown thatthis treatment does not in the least diminish, but, in fact, ratherenhances, the elasticity and flexibility of the elastin tissues.Practice has also shown that the tissues or fibrous constituents of theleather other than the elastin are not afiected by the resin solvent,and hence not prepared to receive a deposit of resin, whereby theleather would otherwise become more or less hard and brittle.

By resin 1 mean not only the common resin obtained in the manufacture ofturpentine, but also those organic compounds of the turpenes whichpossess the property of becoming resinified by oxidation in the air orunder the influence of chemical reagents-i. e., of being converted intosubstances very similar to the resins which occur in nature. Thesenatural resins are solid, amorphous, and generally vitreous brittlemasses of conchoidal fracture, insoluble in water, but soluble inalcohol and other solvents, and are formed naturally and in abundancepartly as balsams, the latter being known as the resins of the balsamseries, and these also can be used in my process.

It is of course not possible to give a fixed proportion of resinrelatively to a given proportion of solvent for general use, as thesenecessarily depend upon the weight of the leather. In the treatment ofheavy leatheras sole-leather, for instancea solution of a resin inbisulfld of carbon or in a hydrocarbon capable of dissolving resin andcontaining from about thirty per cent. to thirty-five per cent. of thelatter will answer the purpose, the percentage of resin being reduced inpro portion to the reduction in the weight of the leather.

The resin solvent being highly volatile, the process is carried out in aclosed vessel or tank provided with suitable racks, from which theleather is suspended, the resin solution being used cold. The leather iscompletely immersed in the solution and is exposed to its action for aperiod of time which likewise varies with the Weight of the leathertreated, the heavier leather requiring about thirty minutes exposure,after which time it is removed and the solvent evaporated. This can bedone either in the open air or in a suitablyheated drying-room.

In my copending application for patent, Serial No. 720,070, I havedescribed a process of treating hides after being prepared for tan= ningin the usual manner and before being tanned substantially similar to theprocess herein described. The action of the resin solvent in the twoprocesses diifers, however, very materially by reason of the vastdifl'er ences in the chemical as well as physical character of thematerials treated. In the treatment of hides as described the resinsolvent acts chemically upon the albuminous tissue of the hide andprepares the tissue for the reception of the resin, which forms thereona protective coating imperceptible to the naked eye, yet suflicient toprotect said tissue against the action of the tanning agent withoutthereby impairing the flexibility of such tissue. The action of theresin solvent and the resin upon leather is, however, radicallydifferent. It is a well-known fact that certain parts of leather, andparticularly the albuminous tissues above referred to, remain unaifectedor are only imperfectlyacted upon by the tanning agent. It is thesetissues which are reacted upon by the resin solvent. By exhaustiveexaminations and tests I believe I succeeded in determining the actionof the solvent and resin upon these tissues, and my conclusions havebeen supported by eminent chemists. When leather is treated as describedand withdrawn from the solution, it has a decidedly-pronounced rubbersmell, and inasmuch as the resin solution itself does not smell likerubber nor does the leather itself previous to its exposure to theaction eso,eoe

of said solution I have come to the conclusion that a chemical reactiontakes place, which I likened to a species of vulcanization in the cold,whereby the untanned or partlytanned albuminous tissues referred to arerendered more elastic or flexible and are at the same time practicallywaterproofed, and these conclusions, as hereinabove stated, have beencorroborated by eminent chemists. It will therefore be seen that thechemical processes which take place in the processes described in thisapplication and in my said copending application are radicallydifferent.

Having thus described my invention, what I claim as new therein, anddesire to secure by Letters Patent, is-

The method of treating leather, which consists in immersing the same fora suitable length-of time in a solution of resin in abisulfid of carbonor in a solution of resin in a hydrocarbon capable of dissolving theresin, for the purpose set forth.

In testimony that I claim the foregoing as my invention I have signed myname in presence of two subscribing witnesses.

VVILLI LISSAUER.

Witnesses SALLY FRIEDLAENDER, WoLnEMAR HAUPT.

